Chrysler Group late today took the unusual step of postponing a planned media drive of the 2014 JeepCherokee scheduled for early next month but vowed that "vehicles will still be in showrooms in September."

The media event -- in which waves of national and foreign journalists were to gather in Seattle between Aug. 8 and 14 to drive the Cherokee for the first time -- was delayed until at least the first half of September, according to an email from the automaker.

"Over the last couple of weeks during final quality and durability testing, we have discovered the opportunity to further improve powertrain calibration" in the Cherokee, the company said.

"We will introduce the vehicle to media and consumers as soon as the process is complete," the automaker said in a statement.

The company maintained that the new SUV would be "in showrooms in September."

The mid-sized Cherokee, a replacement for the Jeep Liberty, is the first Jeep-brand vehicle to be based on a Fiat platform. It will mark the first use of a 9-speed automatic transmission which Chrysler has developed with German supplier ZF Friedrichshafen.

When it arrives in showrooms, the Cherokee will be powered by either a re-engineered 2.4-liter I-4 engine, or a newly developed 3.2-liter V-6 engine.

Production of the Cherokee was originally slated to begin May 23. Instead, Jeep brand head Mike Manley said in late June that production of the Cherokee started on June 24 at the automaker's Toledo assembly complex.

Manley said that the vehicles would be held and not shipped to dealers until the company was confident that there were no problems. He said the new Cherokee would be available to consumers in either August or September, depending on any launch issues.

During a media tour of the plant earlier this month, plant officials said they expected to produce over 400 saleable Cherokees per day by early August and have a full second production shift working by the end of August.

Chrysler CEO Sergio Marchionne visited the Toledo assembly plant last Thursday to speak with workers and inspect Cherokee production. The visit was not open to the media and was not disclosed until after it was completed.